PURPOSE: To simplify work by installing a right and left tilting member and a front and rear mover which are operated with a cylinder on a base on which a leader, such as a pile driver is tiltably mounted on a traveling work car and enabling alignment to be made without moving a chassis.

CONSTITUTION: A right and left tilting member 3 which is operated with a tilting cylinder 4 and a front and rear mover 5 which is operated with a forward and backward moving cylinder 6 are installed on a turning member 54 of a chassis 52 between a bracket 19 which mounts a leader 7 and a base 2. In the case when a pile driver or the like is mounted on the leader 7, the inclination in the front and rear is adjusted under fine control with a derricking cylinder 8 while the inclination on both ways is adjusted under fine control with the mover 5 so that they may be aligned, thereby enabling alignment to be made without moving the chassis 52. This construction makes it possible to make alignment work with ease and safety.